1. Field of the Invention
This invention relates to an overheating preventing method for exhaust purifying devices, whereby the temperature of an internal combustion engine exhaust purifying device such as a catalytic converter is prevented from increasing excessively by adjusting the air-fuel ratio of the exhaust gases.
2. Description of the Prior Art
With known internal combustion engines, it has been the usual practice so that a range of air-fuel ratios at which the temperature of a catalytic converter rises is determined by experiments and the air-fuel ratios in the thus determined range are preset to the rich side to thereby prevent the temperature of the catalytic converter from becoming so high. However, this known construction is disadvantageous in that since a range of enriched air-fuel ratios is predetermined, this range must be selected large enough in consideration of the variations in performance caused by different engines and the increased range tends to result in deteriorated fuel consumption, increased exhaust emissions, etc.